Convert the characters &, <, >, " (double quote), and ' (apostrophe), in a string to their corresponding HTML entities.
convertHTML("Dolce & Gabbana") should return the string Dolce & Gabbana.
convertHTML("Hamburgers < Pizza < Tacos") should return the string Hamburgers < Pizza < Tacos.
convertHTML("Sixty > twelve") should return the string Sixty > twelve.
convertHTML('Stuff in "quotation marks"') should return the string Stuff in "quotation marks".
convertHTML("Schindler's List") should return the string Schindler's List.
convertHTML("<>") should return the string <>.
convertHTML("abc") should return the string abc.